Paul Allen’s appearance on “Charlie Rose” this week wasn’t out of the blue: it was prompted by the release of his new memoir, Idea Man. The book covers the various interests in his life, and while much of the publicity about the book has centered on the passages about co-founding and working at Microsoft with Bill Gates, there is a whole chapter devoted to his interest in space. The bulk of the chapter, after talking about how the early Space Race captured his imagination about the topic, offers some interesting details about the development of SpaceShipOne, the suborbital vehicle he funded that won the $10-million Ansari X PRIZE in 2004.

Allen first met with Burt Rutan in September 1996 in Mojave, Allen recounts in the book. “Burt had already begun thinking about a supersonic plane that could fly above the atmosphere,” Allen writes. Two years later, in Seattle, this idea took the form of a crewed suborbital rocket. At the time, Allen said he had a relatively narrow goal: “I wanted to do something in rocketry that no one had done before.” He was attracted to Rutan because of his perfect safety record, noting that for space tourism to be viable, it would have to have safety “comparable to the airline industry.”

At that time the project didn’t go forward since Rutan hadn’t come up with the “right design”, Allen writes. When Rutan did—the air-launched system with the feathered wings that provide the vehicle a “carefree” reentry—they reached an agreement in 2000, and by 2002 signed a contract creating Mojave Aerospace Ventures (MAV). They were initially not interested in the X PRIZE because it wasn’t funded, but when it became clear shortly after establishing MAV that it would, they changed the design of the vehicle to increase its crew capacity from one to three in order to meet the prize rules. That, Allen said, increased the system’s cost from a projected $9 million to $19 million. “Based on what I’d heard about bleeding-edge aircraft, I expected SpaceShipOne to come in overweight, underpowered, over budget, and behind schedule,” he writes.

While competing for the Ansari X PRIZE, Allen writes that Rutan in particular didn’t think that they had any competition from other teams, calling The da Vinci Project, the Canadian team that eventually made a last-ditch, but futile, effort to beat out SpaceShipOne, “especially far-fetched.” Curiously, Allen writes that they were concerned about “rumored covert efforts in Eastern Europe”, without offering more details.

Much of the rest of the chapter then discusses the development and test flights of SpaceShipOne. Allen was present for the first powered test flight on December 17, 2003, where test pilot Brian Binnie landed SS1 too hard on the runway, causing it to tumble off the runway but without significant damage. That incident, he said, set back their testing schedule by about two months, as they’d hoped prior to that to make the prize-winning flights in the summer of 2004; they instead took place in late September and early October.

After SpaceShipOne’s initial flight into space in June 2004, where the vehicle just barely made it above the von Kármán line (100 kilometers), Allen recalls there were concerns about whether SS1 could do the X PRIZE flights with a heavier load (it had to carry the mass equivalent of three people, although all the flights had only a single person, the pilot, on board). “In fact, SpaceShipOne hadn’t been pushed as close to its limit in June as it had seemed,” he writes. The vehicle was remarkably sturdy, with aerodynamic safety margins of 2.1 to 3 for various components (compared to 1.6 for a typical airliner), and engineers were able to reduce the vehicle’s weight to improve its performance. They also found they could put more nitrous oxide in the vehicle’s oxidizer tank by reducing the ullage, or empty space, that wasn’t needed since the oxidizer didn’t heat up and expand as much as first thought, in part because they took off in the early morning and quickly climbed to higher, colder altitudes.

Allen writes that a month before the June SpaceShipOne flight, Richard Branson approached him about licensing the SpaceShipOne technology. That led to a contract signed in September 2004 “that could net me $25 million over the next fifteen years.” Branson was at the prize-winning flight on October 4, and, as SpaceShipOne was ascending towards space, said to Allen, “Paul, isn’t this better than the best sex you ever had?” Allen didn’t respond, but according to his book he did think, If I was this anxious during any kind of interpersonal activity, I couldn’t enjoy it very much.

Allen could enjoy it, though, when SS1 safely returned and captured the prize. When he heard the roar of the crowd that had assembled in Mojave for the flight, “it struck me that SpaceShipOne was more than some momentary spectacle. It offered hope to everyone who aspired to journeys beyond the Earth.”

In the end, he writes, SpaceShipOne did come in over budget: he said the program’s total cost was $28 million, in the ballpark of previous estimates of its cost. He added that he achieved a “net positive return” on that investment by 2006, thanks to the prize money (he split the $10-million prize with Rutan), the Virgin licensing fees, and also the tax writeoff from donating SpaceShipOne to the Smithsonian’s National Air and Space Museum. “For a time I was tempted to stay involved in the effort to commercialize space tourism,” he writes, but made a decision to step back several months before SS1 won the prize, letting Virgin Galactic take the lead. As he told Charlie Rose earlier this week, he is now considering getting back in.

While Allen has a financial involvement with space tourism ventures, he’s not interested in flying himself. “But seeing up close what’s involved in spaceflight gave me pause. I’m not an edge walker.” What the SpaceShipOne experience did do, though, was restore his “boyhood sense of wonder” he had when he looked at the night sky. “It was good to get it back.”